package com.carl.math;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;

public class question_03 {
    public static void main(String[] args) {
        // 圆的面积
        //solution 1
        final double PAI = 3.14159;
        Scanner sc = new Scanner(System.in);
        double r = sc.nextDouble();
        System.out.printf("S=%.4f",r * r * PAI);

    }
}
